Unsaturated hemiwicking dynamics on surfaces with irregular roughness.

Hypothesis: Spreading of wetting liquids on rough surfaces can occur in a regime termed hemiwicking in which liquid advances ahead of the bulk liquid droplet front under the influence of capillary forces induced by the surface topography. When the surface topography is periodic as in the case for micropillar arrays, the wetting front is sharp and models describing the wetting dynamics can be derived directly from the periodic geometry. For materials with a highly irregular surface topography, the wetting front is diffuse and deriving analytical spreading model parameters directly from the surface topography is not generally possible.

Solvent-Assisted Desorption of 2,5-Lutidine from Polyurethane Films.

A fundamental understanding of chemical interactions and transport mechanisms that result from introducing multiple chemical species into a polymer plays a key role in the development and optimization of membranes, coatings, and decontamination formulations. In this study, we explore the solvent-assisted desorption of a penetrant (2,5-lutidine) in polyurethane with aprotic (acetonitrile) and protic (methanol) solvents. Chemical interactions between solvent, penetrant, and polymer functional groups are characterized via time-resolved Fourier transform infrared spectroscopy (FTIR) during single and multicomponent exposures.

Direct measurement of chemical distributions in heterogeneous coatings.

Chemical warfare agents (CWA) can be absorbed by variety of materials including polymeric coatings like paints through bulk liquid contact, thus presenting touch and vapor hazards to interacting personnel. In order for accurate hazard assessments and subsequent decontamination approaches to be designed, it is necessary to characterize the absorption and distribution of highly toxic species, as well as their chemical simulant analogs, in the subsurface of engineered, heterogeneous materials. Using a combination of judicious sample preparation in concert with scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), it should be possible to directly measure the uptake and distribution of CWA simulants in the subsurface of complex multilayer coatings.

Physics-based agent to simulant correlations for vapor phase mass transport.

Chemical warfare agent simulants are often used as an agent surrogate to perform environmental testing, mitigating exposure hazards. This work specifically addresses the assessment of downwind agent vapor concentration resulting from an evaporating simulant droplet. A previously developed methodology was used to estimate the mass diffusivities of the chemical warfare agent simulants methyl salicylate, 2-chloroethyl ethyl sulfide, di-ethyl malonate, and chloroethyl phenyl sulfide.

Comparison of the internal energy deposition of Venturi-assisted electrospray ionization and a Venturi-assisted array of micromachined ultrasonic electrosprays (AMUSE).

The internal energy deposition of a Venturi-assisted array of micromachined ultrasonic electrosprays (AMUSE), with and without the application of a DC charging potential, is compared with equivalent experiments for Venturi-assisted electrospray ionization (ESI) using the "survival yield" method on a series of para-substituted benzylpyridinium salts. Under conditions previously shown to provide maximum ion yields for standard compounds, the observed mean internal energies were nearly identical (1.93-2.

Electrosonic ejector microarray for drug and gene delivery.

We report on development and experimental characterization of a novel cell manipulation device-the electrosonic ejector microarray-which establishes a pathway for drug and/or gene delivery with control of biophysical action on the length scale of an individual cell. The device comprises a piezoelectric transducer for ultrasound wave generation, a reservoir for storing the sample mixture and a set of acoustic horn structures that form a nozzle array for focused application of mechanical energy. The nozzles are micromachined in silicon or plastic using simple and economical batch fabrication processes.

Analytical performance of a venturi-assisted array of micromachined ultrasonic electrosprays coupled to ion trap mass spectrometry for the analysis of peptides and proteins.

The analytical characterization of a novel ion source for mass spectrometry named array of micromachined ultrasonic electrosprays (AMUSE) is presented here. This is a fundamentally different type of ion generation device, consisting of three major components: (1) a piezoelectric transducer that creates ultrasonic waves at one of the resonant frequencies of the sample-filled device, (2) an array of pyramidally shaped nozzles micromachined on a silicon wafer, and (3) a spacer which prevents contact between the array and transducer ensuring the transfer of acoustic energy to the sample. A high-pressure gradient generated at the apexes of the nozzle pyramids forces the periodic ejection of multiple droplet streams from the device.